Lora message length restriction


I am using AS923 and after a OTAA join, if I send a 20 (or longer) byte message with rui_lora_send, I get error 87. If I keep sending this size message, the error 87 persists.

But if I send a shorter message of 19 bytes or less, the message succeeds.
Here’s the interesting bit, after the first message succeeds I can send the longer messages without issue.

I have also noted the same behaviour using the at+send command (which makes sense as it is probably the same code behind it)

Does anyone know what is happening? Is this something to do with AS923 and DR?

Just want to know if there are some restrictions I am missing about message length.


There is big chance that it is related to DR. The best way is to check the DR at your 1st transmission then check the DR on the 2nd one. Most likely it was changed because ADR is on.

Thanks, I will check it out.

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